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Darth, i do not have the 1.7 ratio rockers. Even if I did I wouldn't be able to use them due to my heads having 10mm threads.
The 1.7's had the factory 8mm threads.
So will the 11/32 .120 will fit you are saying in the LS3 head?
137% stiffer sounds like me when I see a woman I find attractive. This is what I would like to use if they fit.
Would you say the 5/16 .105 is going to be sufficient?
In regards to the peak power, because of the mid length runners, power should be peaking closer to 7000rpm before starting to fall away but as we know it is due to the valvetrain issues.
This actually sounds like a good plan of attack.
Start with the push rods, see what happens,
I'm still thinking this it...
Pushrods first for sure. I would NOT go to 5/16 x .105. That's not enough. The 11/32 will fit. They fit cathedrals even.
I thought you had said you had the YT 1.7's with 10mm upgrade.my bad on that one
The stock heads have enough room to fit a 3/8" pushrod, but it's tight. On my turbo car, I took a drill bit to the pushrod holes in a 5.3L head for a little more clearance and they fit a lot better. My 440ci engine originally had LS3 heads on it and I don’t actually remember having to clearance them for the 3/8” pushrods.
You're awesome. You have a way of saying in three words what takes me sixty.
Haha I tend to be wordy too. I have to go back and edit down my posts lol.
To your other post about the PAC 1209x not being 200# seat pressure, his tuner shimmed them way up to try and get it to pull higher rpm. They’re 500#/in.
Haha I tend to be wordy too. I have to go back and edit down my posts lol.
To your other post about the PAC 1209x not being 200# seat pressure, his tuner shimmed them way up to try and get it to pull higher rpm. They’re 500#/in.
Thanks that explains it
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The stock heads have enough room to fit a 3/8" pushrod, but it's tight. On my turbo car, I took a drill bit to the pushrod holes in a 5.3L head for a little more clearance and they fit a lot better. My 440ci engine originally had LS3 heads on it and I don’t actually remember having to clearance them for the 3/8” pushrods.
I was told by numerous big name shops on here that the pushrods barely fitting and rubbing is not an issue at all. Anyone have any reports of faliure due to rubbing?
Yup. The wall thickness is way less important than the diameter.
I would like to understand this better, care to share? Seems counter intuitive in my brain as a thicker wall should flex less, but I don't have to worry about crazy spring pressure, lobe profiles, or crazy rpm so I'm curious to understand.
Of two tubes with the same wall thickness but different diameters, the larger diameter will be far stiffer then the other.
Two tubes of same diameter but different wall thicknesses, the difference in stiffness will be far less than with the two different diameters.
Of two tubes with the same wall thickness but different diameters, the larger diameter will be far stiffer then the other.
Two tubes of same diameter but different wall thicknesses, the difference in stiffness will be far less than with the two different diameters.
Maybe I just misunderstood the initial post. It sounded, if given a choice, the preference is a larger tube with a thinner wall than a smaller tube with a thicker wall.
Maybe I just misunderstood the initial post. It sounded, if given a choice, the preference is a larger tube with a thinner wall than a smaller tube with a thicker wall.
Bingo! Well sort of. Going from 5/16 heavy wall to 3/8 with the same wall thickness will be a huge improvement, compared to going to a 11/32 with somewhat thicker walls.
Bingo! Well sort of. Going from 5/16 heavy wall to 3/8 with the same wall thickness will be a huge improvement, compared to going to a 11/32 with somewhat thicker walls.
I fully get keeping the same wall thickness, I was trying to understand when the larger diameter is THINNER. Think I found something interesting though. Scaled up but still interesting: A 3 inch diameter steel tube with an 0.062 wall is 18% “stiffer” or deflect 18% less than a 2.5 inch diameter tube with a 0.093 wall thickness and is 7% lighter per foot. · A 2.25 inch diameter tube with an 0.062 wall thickness is about the same stiffness and weights 10% less per foot than the 2 inch 0.093 wall tube.· A 2.5 inch diameter tube with an 0.062 wall thickness is about the same stiffness and weights 27% less per foot than the 2 inch 0.125 wall tube. Answers my question though, there is a crossover point for diameter vs thickness as far as which is stronger.
Resistance to buckling is more impacted by outside diameter than inside diameter of a tube. Cross sectional area is important, as well as the distance from the center axis of that area’s shape.
Larger diameter tubes at a thinner wall thickness can still potentially have more cross sectional area than a thinner diameter with a thicker cross section. Area increases with the square of diameter so material added to the outside of a tube increases cross sectional area exponentially more than material added to the inside.
The area moment of inertia impacts buckling resistance which will get better the further out the material is from its axis - hence getting better with an increase in diameter. The outer ring of material has the greatest contribution to the buckling resistance.
A larger diameter tube with a smaller cross sectional area can have a greater buckling resistance than a smaller diameter with greater CSA.
Columns fail by buckling when their critical load is reached. Long columns can be analysed with the Euler column formula
The pushrod in application is also actually a spring and there are dynamic considerations that are even more complicated. Metal has a spring rate and the pushrod will be compressing and extending as load is applied and released. This oscillation can reach harmonic points that will cause problems in the system if the pushrod is working against the action of the lifter and rocker.
I would like to understand this better, care to share? Seems counter intuitive in my brain as a thicker wall should flex less, but I don't have to worry about crazy spring pressure, lobe profiles, or crazy rpm so I'm curious to understand.
I'll try. Pipe and tubing deflection is a bit effed up, since you need to figure not only cross section but also on moment of inertia (as a structural term, not a kinetic term), resulting in what is called a "Stiffness Factor" (giggedy). But one thing that will surprise you is a 1.75" x .095 wall tube has higher stiffness than a solid 1.25" bar!
First, just on cross-sectional area alone, with no consideration for moment of inertia,
...5/16 x .080 = .0.584 sq in
...5/16 x .100 = 0.0668 sq in
...3/8 x .080 = 0.0741 sq in
...3/8 x .100 = 0.0864 sq in
...11/32 x .125 = 0.0855 sq in
Now, to avoid making the post really long, I'll just calculate moment of inertia (static value, not like the MOI of your flywheel) of the various pushrods at an equal load:
...5/16 x .080 = .0028
...5/16 x .100 = .0029
...3/8 x .080 = .0046
...3/8 x .100 = .0049
...11/32 x .125 = .0039
Now, using moment, I'll calculate the load needed to bend the pushrod (shear, not axial)
...5/16 x .080 = 129 lbs
...5/16 x .100 = 134 lbs
...3/8 x .080 = 210 lbs
...3/8 x .100 = 225 lbs
...11/32 x .125 = 181 lbs
So you see, diameter has WAY more impact than wall thickness on pushrod stiffness. Both in terms of cross section area and moment of inertia. Clear as mud?
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